Tough call. So much going on in both places. She is fluent in French so I give the nod to Paris. I’m a die hard fan of London, but I sometimes feel there are no Brits in London these days. The history is great, but it doesn’t always feel very British, until you get out of the center. I do think it’s easier to get around in London. As far as safety, I think it’s about equal.
She will have a great experience in either city, so she perhaps ought to base her decision on the best program for her needs.